Mankind has been faced since the very beginning with the challenge of finding a way to keep warm while asleep. Since no natural heat is generated due to lack of exercise while asleep, it is necessary to provide additional means of warming or retaining heat while the individual sleeps. Traditionally, of course, this is done by providing a relatively thick or heavy heat insulating cover. The use of electric blankets is now extremely common and provides a source of heat which is generally satisfactory in assuring that an adequate supply of heat during sleeping is available. However, electric blankets suffer from many disadvantages. Among these disadvantages are that the blanket is relatively inefficient, producing substantially more heat than is used by the individual. The blanket is uncomfortable because of the weight and rigidity of the electrical resistance heating lines which extend throughout the blanket. In addition, the individual is forced to accept whatever heat and whatever temperature is generated by the blanket at a given setting. Since the blanket covers the individual, it is not possible to move toward or away from the blanket.
An ancient technique for providing auxilliary heat was to heat bricks, rocks or heavy metal objects, wrap them in blanketing and put them in the bed to warm the bed or to provide auxilliary heat. This is of limited use, but did provide the advantage that the individual could approach the heated object as closely as desired to provide the most comfortable temperature. Heating pads are also available which provide heat for very limited spots.
The present invention overcomes the disadvantages of the electric blanket and of the conventional systems by providing a highly efficient, conveniently configured, and comfortably dimensioned heater which is uniquely adapted to be placed in the bed underneath the insulative covering to provide a source of heat along the length of the user's body, to which the user may approach or retreat, and which can be controlled to temperature.